At least one stimulation electrode line that is typically connected to implantable cardiac pacemakers or defibrillators, and, at its proximal end intended for connection to the cardiac pacemaker or defibrillator, has a standardized electrical terminal, and, at its distal end intended for placement in the heart, has one or more electrode poles. Such an electrode pole is used to deliver electrical pulses to the tissue (myocardium) of the heart or to sense electrical fields in order to sense cardiac activity within the scope of what is known as sensing. For this purpose, electrode poles typically form electrically conductive surface portions of an electrode line. Electrode poles are typically provided as ring electrodes in the form of a ring around the electrode line, or in the form of a point electrode or tip electrode at the distal end of the electrode line. The electrode poles are electrically conductively connected via one or more electrical conductors to contacts of the electrical terminal of the electrode line at the proximal end thereof. One or more electrical conductors, which electrically connect one or more of the electrode poles to one or more of the contacts, thus run between the contacts of the electrical terminal of the electrode lines at the proximal end thereof and the electrode poles at the distal end of the electrode line. These electrical conductors can be used on the one hand for transmission of stimulation pulses to the electrode poles and, on the other hand, for transmission of electrical signals, received by means of the electrode poles, to the proximal end of the electrode line.
If an electrical conductor of the electrode line has a fault, this may mean that the transmission of stimulation pulses to the electrode poles or, in particular, also the transmission of electrical signals from the electrode poles to the proximal end of the electrode line is no longer reliable. In the case of an implantable device in the form of a cardiac pacemaker, this may lead to problems not only in the event of stimulation, but also in the event of sensing, with the result that intracardial events, for example, are not detected or are detected incorrectly. Faults of this type may occur for the first time during the course of operation of the electrode line, that is to say when the electrode line may already have been implanted for a relatively long period of time in a patient. Some implantable devices therefore contain a test apparatus, by means of which faults on the electrode line can be detected, where possible.
Known approaches for electrode fault detection utilize, for example, the measurement and evaluation of the following parameters:
electrode impedances
signal amplitudes
interference signal detection
stimulus thresholds
various plausibility tests
The known methods for electrode fault detection continually demonstrate low sensitivity and specificity, however. For example, insulation defects on the electrode line thus may not be established at all by means of an impedance measurement, since the impedance of the actual electrode poles is much lower than a reduction of the impedance as a result of an insulation defect, such that the insulation defect leads only in the impedance test to an insignificant drop of the measured impedance. The same is true for the other mentioned methods.
The present invention is directed toward overcoming one or more of the above-mentioned problems.